Conventionally, an analog-to-digital converter (ADC) is provided for the purpose of converting an analog signal from a sensor or an antenna into a digital signal in various electronic devices that perform measurement and wireless communication. Among various types of ADCs, successive approximation register-type ADC (SARADC) is widely used due to its advantage of low power consumption and a small circuit scale.
Additionally, SARADC can be classified into a differential SARADC performing AD conversion of a differential signal and a single-ended SARADC performing AD conversion of a single-ended signal. Among them, the differential SARADC has higher symmetry between the positive-side circuit and the negative-side circuit compared with the single-ended SARADC, making it possible to suppress the noise and fluctuation of the power supply voltage. For this reason, it is desirable to perform AD conversion using a differential SARADC. However, when AD conversion is performed on a single-ended signal using a differential SARADC, it is necessary to preliminarily convert a single-ended signal into a differential signal by using a single-ended-to-differential conversion circuit. For example, there is proposed a single-ended-to-differential conversion circuit that performs conversion to a differential signal by a circuit provided with two stages of operational amplifiers, resistors, and the like (for example, refer to Non-Patent Document 1).